Hennessey Performance took the opportunity at last week's Specialty Equipment Market Association show in Las Vegas to tout its Venom F5, which it claimed will set a world speed record of 301 mph.

Swedish supercar maker Koenigsegg, on the other hand, headed out of town to a straight stretch of road blocked off by the Nevada Highway Patrol and put the hammer down in one of the company's 1,341-horsepower Agera RS rockets.

Koenigsegg

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The resulting in-car video shows a certified 284 mph on the second pass, with a two-way official average speed (to account for wind and any grade to the road) of 277.9 mph, breaking the previous record of 267.9 mph for production models held by the Bugatti Veyron Super Sport.

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The truly astonishing part of the video, aside from the blurred scenery at top speed, is the ease with which the driver accelerated up to speed, not shifting into top gear and flooring the accelerator until 220 mph, when the car launches like he'd lit the afterburner.

Koenigsegg

Maybe just as amazing is how your perception shifts. During the coast down period after reaching top speed, as the car slows down to the 200 mph pace that so many supercars strain to achieve as their top speeds, the Agera RS seems to have crawled nearly to school-zone speed.

It must be quite a thrill to wheel such a beast at these speeds, judging from the whoop driver Niklas Lilja gives out during the coast-down.